JP2001355126A - Polyurethane fiber and stretch fabric highly resistant to alkali, and method for alkali reduction treatment of stretch fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stretch fabric slight in powderdown when subjected to alkali reduction treatment, and to provide a polyurethane fiber to be used in producing such a stretch fabric. SOLUTION: This stretchable fabric is obtained by using a polyurethane fiber >=80% in mechanical strength retention when treated at 130 deg.C for 60 min in an aqueous solution containing 50 g/L caustic soda.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyurethane fiber and a stretchable fabric which are excellent in alkali resistance used for a process for reducing the weight of a fiber product, and a method for reducing the alkali content of a stretchable fabric.

[0002]

2. Description of the Related Art Polyurethane fibers produced from polyurethane using polyisocyanate, polymer diol, and low molecular weight polyfunctional active hydrogen compound as raw materials are extensible,
Because of its excellent elastic properties such as recoverability and resilience, it is widely used in applications requiring elasticity such as women's underwear, swimwear and stockings. Polyurethane fiber is rarely used alone, and is used as an elastic fabric by knitting and weaving with other materials such as polyester fiber. In combination with polyester fiber, weight reduction processing of polyester fiber is performed for the purpose of improving the texture of the fabric. However, when a fabric containing polyurethane fibers is subjected to weight reduction processing, the power of the fabric often decreases.

[0003]

The problem to be solved by the present invention is to provide a stretchable fabric having improved power down in alkali weight reduction processing, a polyurethane fiber used for the stretchable fabric, and a method of reducing the alkali weight of the stretchable fabric. Offer.

[0004]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that the alkali used in the alkali weight reduction processing of the fabric reduces the strength of the polyurethane fiber.
Furthermore, they have found that the strength of a polyurethane fiber containing a specific additive does not decrease due to alkali, leading to the completion of the present invention.

That is, the present invention provides (1) a polyurethane fiber having a tenacity retention of 80% or more when treated at 130 ° C. for 60 minutes in an aqueous solution containing 50 g / l of caustic soda; and (2) The polyurethane fiber according to (1), wherein the polyurethane fiber contains a hindered amine compound, a phosphite compound, and a phenolic antioxidant, and (3) the hindered amine compound is represented by the following formula (1): It contains a repeating unit represented by the following formula (2) and a repeating unit represented by the following formula (2), and has a ratio of the number of repeating units represented by the following formula (1) to the number of repeating units represented by the following formula (2). Is 0.3
5 or more and 1.75 or less, and the sum of the number of repeating units represented by the following formula (1) and the number of repeating units represented by the following formula (2) is 2 or more and 10,000 or less. The polyurethane elastic fiber according to claim 2, wherein

[0006]

Embedded image

[0007]

Embedded image [In the above formula, R ¹ represents a methyl group or a hydrogen atom, and R ^{2 to} R
⁵ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that all are not hydrogen atoms. R ⁶ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an oxyalkyl group, R ⁷ represents a methyl group or a hydrogen atom;
⁸ represents a cycloalkyl group having 5 to 10 carbon atoms or an alkyl group having 10 to 30 carbon atoms, and X and Y each represent an -O- group or -NH- group. ], And
(4) In the method of (1) to (3), wherein the stretchable fabric containing the polyurethane fiber according to any one of (1) to (3), and (5) the method of reducing the alkali weight of the stretchable fabric, the stretchable fabric is changed from (1) to (3) A method for reducing the alkali weight of a stretchable fabric, characterized by comprising the polyurethane fiber described in (1).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyurethane fibers in the present invention can be produced from known polyurethanes such as polyethers, polyesters and polycarbonates. Such a polyurethane can be obtained by reacting a polyisocyanate, a polymer diol and, if desired, a low-molecular polyfunctional active hydrogen compound.

As the polyisocyanate, for example, 4,
4'-diphenylmethane diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, 1,4-cyclohexane diisocyanate, 4,
One of 4′-dicyclohexylmethane diisocyanate, xylylene diisocyanate and the like, or a mixture thereof can be used. Among them, 4,4′-diphenylmethane diisocyanate is preferred.

The polymer diol is a substantially linear polymer having a hydroxyl group at both terminals and having a molecular weight of 600 to 7000, for example, polytetramethylene ether glycol, polypropylene ether glycol, polyethylene ether glycol, polypentamethylene ether glycol. Such as polyether polyols, copoly (tetramethylene neopentylene) ether diol, copoly (tetramethylene-2-methylbutylene) ether diol, copoly (tetramethylene / 2,3-dimethylbutylene) ether diol, copoly (tetramethylene A copolyether polyol containing two or more alkylene groups having 6 or less carbon atoms such as (2,2-dimethylbutylene) ether diol, adipic acid, sebacic acid,
Maleic acid, itaconic acid, azelaic acid, malonic acid, succinic acid, glutaric acid, suberic acid, dodecanedicarboxylic acid, β-methyladipic acid, one or a mixture of two or more dibasic acids such as hexahydroterephthalic acid Ethylene glycol, 1,2-propylene glycol, 1,4-
Polyester polyol obtained from one or a mixture of two or more glycols such as butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-dimethylolcyclohexane, polyetherester diol, polylactone diol, and polycarbonate Any polyol, such as a diol, can be used. Among them, polyether diols are preferred.

Examples of the low molecular weight polyfunctional active hydrogen compound include compounds having two or more active hydrogen groups capable of reacting with an isocyanate group in the molecule (chain extenders).
As a chain extender, for example, ethylenediamine, 1,2-
Diaminopropane, 1,3-diaminopropane, 1,4
-Diaminopropane, diethylenetriamine, polyamines such as triethylenetetramine, ethylene glycol, polyols such as butanediol, polyhydrazide, polysemicarbazide, polyhydroxylamine,
One or a mixture of two or more of water, hydrazine and the like can be mentioned. Among them, ethylenediamine is preferred.

A compound having only one active hydrogen group capable of reacting with an isocyanate group in the molecule can be used in combination with a chain extender as a terminal terminator. Compounds having only one active hydrogen group in the molecule include dialkylamines such as diethylamine, dimethylamine, dibutylamine and diethanolamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, t-butylamine, ethanol One or more kinds of monoalkylamines such as amines, monols such as n-butanol, dehydration condensates of diamines and ketones such as a 1: 1 reaction product of ethylenediamine and acetone, and N, N-dimethylhydrazine; Mixtures can be mentioned.

The polyurethane can be polymerized by a known method. For example, it can be polymerized by any method such as melt polymerization, solution polymerization and the like, and a combination thereof. In addition, an arbitrary method such as a one-shot method in which raw materials are mixed and reacted at once, or a prepolymer method in which a prepolymer is first formed and a chain is extended can be used. In addition, an appropriate amount of an organic acid such as acetic acid or p-toluenesulfonic acid, carbon dioxide, or the like may be added as a reaction rate regulator at an arbitrary stage during the polymerization reaction. These reaction modifiers are preferably added after the completion of the prepolymer reaction and before the completion of the chain extension reaction. Further, these reaction rate regulators may be added as a mixture with a chain extender or a terminal terminator.

The polyurethane fiber can be produced from polyurethane by any known method such as a dry spinning method, a wet spinning method and a melt spinning method.

The polyurethane fiber in the present invention is not particularly limited, but a polyurethane fiber containing a hindered amine compound, a phenolic antioxidant and a phosphite antioxidant is preferable. The hindered amine compound generally refers to a polyalkyl-substituted piperidine derivative. As the hindered amine compound,
Any known compound can be used. The hindered amine compound preferably has a solubility in an acidic aqueous solution of pH 4 of 5.0 × 10 ⁻³ eq / liter or less. The molecular weight of the hindered amine compound is not particularly limited, but is preferably 1,000 or more and 1,000,000 or less. It is more preferably 10,000 or more and 500,000 or less. The number of piperidyl groups in the hindered amine compound is not particularly limited.
It is preferable to contain 1.3 mol or more per unit. The amount of the hindered amine compound is not particularly limited, but is preferably 0.1 to 5% by weight with respect to the polyurethane. The time of blending the hindered amine compound with the polyurethane is not particularly limited as long as it is up to spinning,
It is preferable to mix after the polymerization of polyurethane is completed.

Preferred examples of the hindered amine compound include a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2).
The ratio of the number of repeating units represented by the following formula (1) to the number of repeating units represented by the formula is 0.35 or more and 1.7.
And hindered amine compounds in which the total number of repeating units represented by the following formula (1) and the number of repeating units represented by the following formula (2) is 2 or more and 10,000 or less.

[0017]

Embedded image

[0018]

Embedded image [In the above formula, R ¹ represents a methyl group or a hydrogen atom, and R ^{2 to} R
⁵ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that all are not hydrogen atoms. R ⁶ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an oxyalkyl group, R ⁷ represents a methyl group or a hydrogen atom;
⁸ represents a cycloalkyl group having 5 to 10 carbon atoms or an alkyl group having 10 to 30 carbon atoms, and X and Y each represent an -O- group or -NH- group. In formula (1), R ^{2 to} R ⁵ are preferably all methyl groups, and R ⁶ is preferably a methyl group or a hydrogen atom. R ⁸ in the formula (2) is preferably a cycloalkyl group. X and Y in Expressions (1) and (2)
Are preferably -O- groups. The above preferred hindered amine compound may have a structure other than the formulas (1) and (2), and the content thereof is as follows.
20% by weight or less in the hindered amine compound is preferable,
It is more preferably at most 5%, and still more preferably 0%.
%. If the content is 20% by weight or more, it becomes impossible to express well the stability before and after various processes in a well-balanced manner.

The hindered amine compound in the present invention is a group in which all or a part of the hindered amino group comprises an organic carboxylic acid, carbon dioxide, a phosphoric acid compound, a phosphoric acid ester compound, a phosphorous acid compound, and a phosphite compound. One or more compounds selected from the above may form a salt. All or part of the hindered amino group of the hindered amine compound, by forming a salt with the above compound, adjusts the basicity and solubility of the hindered amine compound without impairing the stabilizing effect inherent to the hindered amine compound. be able to.

The organic carboxylic acid may have 1 to 10 carbon atoms.
Is preferred, and a saturated carboxylic acid is preferred. Further, monocarboxylic acids are preferable to polycarboxylic acids. Specific examples include formic acid, acetic acid,
Propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, acetoacetic acid, pyruvic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, benzoic acid, naphthoacetic acid, phenyl Acetic acid and the like can be mentioned.

The phosphoric acid compound refers to phosphoric acid or a salt of phosphoric acid with a basic compound such as an amine or a metal ion. The phosphorous acid compound refers to phosphorous acid or a salt of phosphorous acid with a base compound such as an amine or a metal ion. The phosphate ester compound is preferably a phosphate monoester compound or diester compound, but may be a polymer compound having a phosphate monoester or diester structure partially. As the phosphite compound, a phosphite monoester compound or a diester compound is preferable, but a high molecular compound and a compound partially having a phosphite monoester or diester structure may be used. Good. The phosphate compound and the phosphite compound may be partially a salt with a base compound such as an amine or a metal ion.

As the phenolic antioxidant, any known phenolic antioxidant can be used. In consideration of solubility in solvents and compatibility with polyurethane,
Appropriate compounds can be selected. Examples of phenolic antioxidants include pentaerythritol-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] and octadecyl-3- (3,5
-Di-t-butyl-4-hydroxyphenyl) propionate, 1,1,3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-
Tris (4-t-butyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 1,3,5-tris (4-s
ec-butyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 1,3,5-tris (4-neopentyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 2,2′-methylenebis (4 -Methyl-6-t-butylphenol), 4,4'-butylidenebis (4-methyl-6-t-butylphenol), 1,3,5-trimethyl-2,4,6-tris (3,5-di- t-butyl-4-hydroxybenzyl) benzene, tris- (3,
5-di-t-butyl-4-hydroxybenzyl) -isocyanurate, 3,9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy) -1, 1-dimethylethyl] -2,4
8,10-tetraoxaspiro [5,5] undecane,
Triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5
-Di-t-butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamide), 3,5-di- t-butyl-4-hydroxybenzylphosphonate-diethyl ester, tris-
(3,5-di-t-butyl-4-hydroxybenzyl)
-Isocyanurate, isooctyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-bis [3- (3,5-di-t-butyl-
4-hydroxyphenyl) propionyl] hydrazine,
Examples include a polycondensate of p-chloromethylstyrene and p-cresol, a polycondensate of p-chloromethylstyrene and divinylbenzene, and an isobutylene reaction product of p-cresol and divinylbenzene polycondensate. Among them 1,
3,5-tris (4-t-butyl-3-hydroxy-
2,6-dimethyl) isocyanuric acid, 1,3,5-tris (4-sec-butyl-3-hydroxy-2,6-dimethyl) isocyanuric acid, 1,3,5-tris (4-neopentyl-3- Hydroxy-2,6-dimethyl) isocyanuric acid is particularly preferred and 1,3,5-tris (4-
Most preferred is t-butyl-3-hydroxy-2,6-dimethyl) isocyanuric acid. Further, two or more phenolic antioxidants may be used in combination. The compounding amount of the phenolic antioxidant is 0.
It is preferably between 1 and 2% by weight.

As the phosphite compound, any known compound can be used. An appropriate compound can be selected in consideration of solubility in a solvent, compatibility with polyurethane, and the like. Examples of the phosphite compound include tetrakis (2,4-di-t-butylphenyl) -4,4′-biphenylenephosphonite, tris (nonylphenyl) phosphite, and tris (2,4
-Di-t-butylphenyl) phosphite, distearylpentaerythritol diphosphite, di (2,4
-Di-t-butylphenyl) -pentaerythryl diphosphite, di (2,6-di-t-butyl-4-methylphenyl) -pentaerythryl diphosphite,
Triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, 4,
4'-butylidene-bis (3-methyl-6-t-butylphenyl-ditridecyl) phosphite, cyclic neopentanetetrayl (octadecyl phosphite), tris (mono and / or dinonyl phenyl)
Phosphite, diisodecylpentaerythritol diphosphite, 2,2-methylenebis (4,6-di-t-
(Butylphenyl) octyl phosphite, bis (tridecyl) pentaerythritol diphosphite, bis (nonylphenyl) pentaerythritol diphosphite, hydrogenated bisphenol A / pentaerythritol
Phosphite polymer, hydrogenated bisphenol A phosphite polymer, tetraphenyl tetra (tridecyl)
Pentaerythritol tetraphosphite, tetra (tridecyl) -4,4′-isopropylidene diphenyl diphosphite, tetraphenyl dipropylene glycol diphosphite and the like can be mentioned. Of these, hydrogenated bisphenol A / pentaerythritol phosphite polymer and hydrogenated bisphenol A phosphite polymer are preferred. Further, two or more phosphite compounds may be used in combination. The compounding amount of the phosphite compound is 0.1 to 2 with respect to the polyurethane.
Preferably it is between wt.%.

The polyurethane fiber of the present invention may contain known additives as necessary. For example, hindered amine-based, hindered phenol-based, thioether-based, phosphite-based, lactone-based antioxidants, benzotriazole-based, benzophenone-based, oxalic anilide-based ultraviolet absorbers, hydrazine derivatives, oxalic acid derivatives and the like Metal deactivators, barium sulfate, magnesium silicate, calcium silicate, participating zinc, magnesium oxide, hydrotalcite and derivatives thereof, titanium dioxide, inorganic fine particles such as molybdenum sulfide, magnesium stearate, calcium stearate, higher fatty acid amide, Contains anti-adhesives such as higher fatty acid esters, higher alcohols, polyorganosiloxanes, and polytetrafluoroethylene, as well as fungicides, antibacterials, flame retardants, and bluing agents such as blue pigments, fluorescent brighteners, and blue dyes. can do The method of mixing these additives with the polyurethane polymer is not particularly limited, and can be blended by any known method. The compounding can be performed at any stage during the production of the polyurethane, but it is preferable that the compounding is performed after the completion of the polyurethane polymerization and before the spinning step.

The polyester fiber used together with the polyurethane fiber in the stretchable fabric of the present invention is a polyester fiber known to those skilled in the art, and a typical example is polyethylene terephthalate. The polyamide fibers used in the stretchable fabric of the present invention include nylon 6, nylon 66, nylon 46, and their cationic dyeable denatured products and polyamide / ester composite fibers, and those having any fineness and cross-sectional shape. Can be used.

The cellulosic fiber used together with the polyurethane fiber in the stretchable fabric of the present invention includes cotton yarn, rayon, a blend yarn of these with polyester fiber, a composite yarn of nylon / ester long fiber, and the like. You can choose the fineness.

The fibers used in combination with the polyurethane fibers in the stretchable fabric of the present invention are not limited as long as they are inelastic yarns. Animal hair fibers such as wool, cashmere and alpaca, silk, acrylic fibers, Fibers such as promix fibers are also used.

The polyurethane fiber used in the stretchable fabric of the present invention is usually used in the form of a bare (bare) yarn, or a composite elastic yarn such as a single covering yarn, a double covering, a core spun yarn, and a pliers. . The stretchable fabric targeted in the present invention is a stretchable woven or knitted fabric composed of the polyurethane elastic yarn and the above-mentioned polyester-based fiber, polyamide-based fiber, and inelastic yarn such as cellulose-based fiber. And / or plain weave, twill weave, satin weave and the like used for the weft. In the case of knitting, circular knitting is a flat knit, double-sided knitting, rib knitting, pearl knitting or a change knitted fabric thereof, and warp knitting is a tricot knitted fabric or Russell knitted fabric, and is not particularly limited. As a knitting structure, in case of tricot knitted fabric, half net, reverse half knit, double denby knit, double atlas knit, power net, half power net, satin net,
A triconet or the like can be exemplified.

[0029]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the scope of these examples. Parts and% in the examples represent parts by weight and% by weight, respectively.

(Evaluation method for alkali resistance) A 2 liter aqueous solution of caustic soda having a concentration of 50 g / liter and a polyurethane fiber held in a fixed length in a fixing jig were placed in a 3 liter pot, and a mini-color dyeing machine was prepared. Using (Texam Giken Co., Ltd.), the temperature was raised to 130 ° C. at a rate of 2 ° C./min, followed by treatment for 60 minutes. Thereafter, the pot was cooled, the polyurethane fiber was taken out, washed with water, and air-dried.
The strength (stress at break) of the yarn before and after the treatment was measured by a tensile tester, and the percentage of the strength after the treatment to the strength before the treatment was defined as the strength retention.

(Synthesis Example 1): Synthesis of Hindered Amine Compound 2,2,6,6 was placed in a 500 cc branched flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser.
60 parts of tetramethyl-4-piperidyl methacrylate (ADEKA STAB LA-87 / Asahi Denka Kogyo Co., Ltd.), 40 parts of cyclohexyl methacrylate, and 213 parts of N, N-dimethylacetamide were taken and dissolved by stirring.
The flask was heated in an oil bath with stirring to 60 ° C. while bubbling nitrogen through. After reaching 60 ° C,
2,2'-azobis (isobutyronitrile) (AIB
N) 0.8 part was added. The reaction was maintained at 60 ° C. while stirring as it was. Five hours after the initial addition of AIBN, an additional 0.2 parts of AIBN was added. 6 more reactions
After continuing at 0 ° C. for 15 hours, the reaction was terminated by cooling to room temperature to obtain a hindered amine compound solution. The solution viscosity measured with an E-type viscometer at 30 ° C. using a rotor having a cone angle of 3 ° and a radius of 14 mm was 15 poise. The unreacted polymerizable monomer in the solution was quantified by gas chromatography and found to be 4% by weight based on the weight of the charged polymerizable monomer. The absolute molecular weight of the hindered amine compound measured by GPC-LALLS was 110,000. When the ¹ H-NMR spectrum of the obtained hindered amine compound was measured at 50 ° C. using a 1: 1 mixture of DMSO-d ₆ and CDCl ₃ as a solvent, the proton of the methine carbon of the piperidyl group and the proton of the methine carbon of the cyclohexyl group were: 5.0, 4. It was detected at 6 ppm, and the integral ratio was 52:48. This integral ratio is calculated as 2,2,6,6-tetramethyl- in the hindered amine compound.
Since it is considered to be the molar ratio of the unit derived from 4-piperidyl methacrylate to the unit derived from cyclohexyl methacrylate, the weight fraction of each is calculated to be 60,40% by weight, which matches the value obtained from the charged amount. did.

(Example 1) 175.37 parts of polytetramethylene ether glycol having a number average molecular weight of 1800 and 4,4'-diphenylmethane diisocyanate 38.9
Two parts were reacted at 80 ° C. for 3 hours under a stream of N ₂ to obtain a prepolymer having both ends isocyanate groups. After cooling the prepolymer to 40 ° C., 308.36 parts of N, N-dimethylacetamide was added and dissolved, and further cooled to 10 ° C. 3.58 parts of ethylenediamine and 0.46 parts of diethylamine were combined with N, N-dimethylacetamide.
The solution dissolved in 86 parts was added at a time to the prepolymer solution with high speed stirring and mixed to complete the reaction. The viscosity at 30 ° C. of this solution was 2000 poise.
To this solution, 13.42 parts of the hindered amine compound solution obtained in the above Synthesis Example, 1,3,5-tris (4-t-
2.15 parts of butyl-3-hydroxy-2,6-dimethylbenzyl isocyanurate (Cyanox 1790 / Nippon Cyanamid), hydrogenated bisphenol A / pentaerythritol phosphite polymer (JPH-3)
800 / Johoku Chemical Co., Ltd.) 2.15 parts, 2-[(2-hydroxy-3,5-di-t-amyl) phenyl] benzotriazole (KEMISORB74 / Chempro Chemical Co., Ltd.) 1.08 parts, and magnesium stearate 0.
69 parts were added and mixed with stirring to obtain a polyurethane solution.
After defoaming the polyurethane solution, 230 μm
The air heated to ° C. was extruded into the spinning cylinder, and wound while applying an oil agent to obtain a polyurethane fiber of 44 dtex.

Comparative Example As a comparative example, 4.30 parts of a polyaddition product of 4-t-butyl-4-aza-2,6-heptanediol and methylene-bis (4-cyclohexyl isocyanate) and p- The evaluation was performed using a polyurethane fiber containing 2.15 parts of a copolymer of cresol and divinylbenzene.

Table 1 shows the strength retention of polyurethane fibers when treated with alkali in each of the examples and comparative examples. It can be seen that the polyurethane elastic yarn of the present invention has high resistance to alkali and is particularly suitable for use in fabrics in which the weight of alkali is reduced.

[0035]

[Table 1]

[0036]

As described above, by using the polyurethane fiber of the present invention, it is possible to obtain an excellent stretchable fabric with less power down due to alkali weight reduction processing.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) D03D 15/08 D03D 15/08 D04B 1/18 D04B 1/18 21/00 21/00 B // (C08L 75/04 (C08L 75/04 33:14 33:14 33:24) 33:24) (72) Inventor Toru Okada 2-1-1 Katata, Otsu, Shiga Prefecture F-term in Toyobo Co., Ltd. Ref.

Claims (5)

[Claims] 1. A polyurethane fiber having a tenacity retention of 80% or more when treated at 130 ° C. for 60 minutes in an aqueous solution containing 50 g / l of caustic soda. 2. The polyurethane fiber according to claim 1, wherein the polyurethane fiber contains a hindered amine compound, a phosphite compound, and a phenolic antioxidant. 3. The hindered amine compound contains a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2), and is based on the number of repeating units represented by the following formula (2). The ratio of the number of repeating units represented by the following formula (1) is 0.35 or more and 1.75 or less;
The polyurethane elasticity according to claim 2, wherein the total of the number of repeating units represented by the following formula (1) and the number of repeating units represented by the following formula (2) is 2 or more and 10000 or less. fiber. Embedded image Embedded image [In the above formula, R ¹ represents a methyl group or a hydrogen atom, and R ^{2 to} R
⁵ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that all are not hydrogen atoms. R ⁶ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an oxyalkyl group, R ⁷ represents a methyl group or a hydrogen atom;
⁸ represents a cycloalkyl group having 5 to 10 carbon atoms or an alkyl group having 10 to 30 carbon atoms, and X and Y each represent an -O- group or -NH- group. ] 4. An elastic fabric comprising the polyurethane fiber according to claim 1. 5. A method for reducing the alkali content of a stretchable fabric, wherein the stretchable fabric contains the polyurethane fiber according to claim 1 or 3.